Managing Storage Space in Storage Systems

1. A method for use in managing storage space in storage systems, the method comprising: evaluating metadata of a slice of a storage pool in a data storage system for returning the slice as free storage to the storage pool; and based on the evaluation, affecting returning of the slice to the storage pool, wherein the metadata of the slice indicates whether the slice includes user data, wherein affecting returning of the slice to the storage pool further comprising avoiding updating contents of the slice upon determining that the slice does not include user data.

2. The method of claim 1 , wherein an auto-tiering policy engine identifies a set of slices for relocation, wherein the slice is a logical representation of a subset of physical disk storage.

3. The method of claim 1 , wherein a storage tier includes a disk drive system comprising a plurality of Redundant Array of Inexpensive Disks (RAID) systems, each RAID system of the plurality of RAID systems having a first disk drive and a second disk drive.

4. The method of claim 1 , wherein the metadata of a slice includes a slice map entry, wherein the slice map entry includes an empty slice bit, wherein the empty slice bit indicates whether the slice includes user data.

5. The method of claim 1 , wherein a file system mapping driver provides information to a mapped LUN driver, wherein the information indicates whether a slice includes user data.

6. The method of claim 1 , wherein an empty slice indicates that the empty slice does not include user data.

7. The method of claim 1 , further comprising: determining whether the slice is an empty slice; and based on the determination, writing zeroes to the slice before returning the slice to the storage pool.

8. The method of claim 1 , further comprising: determining whether the slice is an empty slice; and based on the determination, avoid writing zeroes to the slice before returning the slice to the storage pool.

9. The method of claim 1 , further comprising: determining whether the slice includes user data; and based on the determination, returning the slice to the storage pool without updating contents of the slice.

10. A system for use in managing storage space in storage systems, the system comprising: first logic evaluating metadata of a slice of a storage pool in a data storage system for returning the slice as free storage to the storage pool; and second logic affecting, based on the evaluation, returning of the slice to the storage pool, wherein the metadata of the slice indicates whether the slice includes user data, wherein affecting returning of the slice to the storage pool further comprising: third logic avoiding updating contents of the slice upon determining that the slice does not include user data.

11. The system of claim 10 , wherein an auto-tiering policy engine identifies a set of slices for relocation, wherein the slice is a logical representation of a subset of physical disk storage.

12. The system of claim 10 , wherein a storage tier includes a disk drive system comprising a plurality of Redundant Array of Inexpensive Disks (RAID) systems, each RAID system of the plurality of RAID systems having a first disk drive and a second disk drive.

13. The system of claim 10 , wherein the metadata of a slice includes a slice map entry, wherein the slice map entry includes an empty slice bit, wherein the empty slice bit indicates whether the slice includes user data.

14. The system of claim 10 , wherein a file system mapping driver provides information to a mapped LUN driver, wherein the information indicates whether a slice includes user data.

15. The system of claim 10 , wherein an empty slice indicates that the empty slice does not include user data.

16. The system of claim 10 , further comprising: third logic determining whether the slice is an empty slice; and fourth logic writing, based on the determination, zeroes to the slice before returning the slice to the storage pool.

17. The system of claim 10 , further comprising: third logic determining whether the slice is an empty slice; and fourth logic avoid writing, based on the determination, zeroes to the slice before returning the slice to the storage pool.

18. The system of claim 10 , further comprising: third logic determining whether the slice includes user data; and fourth logic returning based on the determination, the slice to the storage pool without updating contents of the slice.